This invention relates generally to electronic steering, and more particularly to a variable resistance system for electronic steering.
Conventional electronic steering uses a position sensor to detect the rotational position of a steering wheel. The position sensor transmits a position signal to an actuating device, e.g., a hydraulic pump or a microprocessor that controls the hydraulic pump in the case of electro-hydraulic steering systems, which then moves the wheels of the machine to the appropriate position. Often, conventional mechanical stops are coupled to the shaft of the steering wheel to prevent movement beyond a particular angle from the xe2x80x9cstraight aheadxe2x80x9d steering position.
One problem with including a mechanical stop is that the amount of rotation of the steering wheel is determined at the time the machine having the steering wheel is assembled, and cannot be changed without substantial rework, if at all.
In addition, if different degrees of rotation are desired for the steering wheels of two machines in the same product line, e.g., wheel loaders, then multiple components must be stocked. This additional inventory increases the expense for the manufacturer.
A second problem with electro-type/electronic steering systems is that the resistance to movement of the steering wheel is in many cases, constant. Some electro-type/electronic steering systems increase the resistance as vehicle speed increases, and others increase the resistance as the difference between the commanded wheel position (from the steering wheel) and the actual wheel position, but little else is done to provide feedback or to affect the way the operator controls the steering wheel.
The present invention provides apparatus and methods for controlling the resistance to the movement of a steering shaft that is operable to move as a function of an operator input. A position sensor is coupled with the steering shaft and transmits a shaft position signal as a function of the position of the steering shaft. A processing device is coupled with the position sensor to receive the shaft position signal and transmits a resistance signal as a function of the shaft position signal. A resistance device is coupled with the processing device to receive the resistance signal and is coupled with the steering shaft, the resistance device resists the movement of the steering shaft as a function of the resistance signal.